Optically active, magnetic gels consisting of helical substituted polyacetylene and Fe3O4 nanoparticles: preparation and chiral recognition ability

This paper reports the preparation of unique composite gels demonstrating both optical activity and magnetic responsivity (the gels are denoted as OAMGs). The composite gels consist of magnetic Fe3O4 nanoparticles (Fe3O4 NPs) and helical substituted polyacetylene with a predominantly one-handed screw sense. The former provides magnetic responsivity, while the latter provides optical activity. The OAMGs were synthesized from alkyne-modified Fe3O4 NPs and substituted acetylene monomer (M1) via coordination polymerization by using (nbd)Rh+B−(C6H5)4 as a catalyst and dipropargyl adipate (M3) as a crosslinker. The substituted polyacetylene chains in the gels adopted helical structures of preferential helicity, according to circular dichroism and UV-vis absorption spectroscopy. The gel (Gel-3) showed a high saturation magnetization of 21.2 emu g−1 and rapid magnetic responsivity. The gel also demonstrated a preferential adsorption toward the (R)-(+)-1-phenylethylamine of the two enantiomers. After use, the gels can be easily recycled simply with the assistance of an external magnetic field, indicating the potential applications of the novel gels in chiral resolution, enantioselective-controlled release, chiral reactors for asymmetric catalysis, etc.